Microphone.



A VAUGEAN, A. DE LAVANDEYRA & W. 'GARTHWMTE.

MICROPHONE. APPLICATION FILED OCT- 15. 1915.

355 Patentedlune 26,1917.

2 SHEETS SHEET I.

Fig.1

A. VAUGEAN, A. DE LAVANDEYRA 8: W. GARTHWAITE.

MICROPHONE.

APPLICATION FILED 00115. 1915.

l 93@,95& Patented J 11116 26, 1917.

Fig.6

2 SHEETS-SHEET 2.

' crophone formed ALEXANDBE VAUGEAN, ANTHONY mt LAVANDEYRA,

AND WILLIAM GARTHWAITE, 0F

PARIS, FRANCE.

MICROPHONE.

Specification of Letters Patent. Patented June 26, 1917'.

Application filed October 15, 1915. Serial No. 56,107.

To all whom it may concern: I

Be it known that we, ALEXANDRE VAP- GEAN, subject of the King ofRomania, 'ANTHoNY DE LAvANDnm, citizen of the Republic of Brazil, andWILLIAM GARTHWAITE, subject of the King of ing the first at 18 Rue SaintSenoch, Paris, France, the second at 9 Rue Lo Dellbes, Paris, France,the third at 7 Rue Meyerbeer, Paris, France, have'invented a new anduseful Improvement in Microphones, which improvement is fully set forthin the following specification. v

This invention relates to microphones for use in telephony. Reduced toits simplest expression, the theory of the microphone is contained inthe three words a variable resistance. Usually this variable resistanceis obtained by varlable intensity'of pressure exerted by the action ofthe sound waves on the imperfect contacts of several carbon elements.The agglomerations of carbon possess in fact the property of having aconductibility which is variable according to the degree of pressure .towhich their points of contact are subjected. 1

If the fact is considered that the variable resistance of a microphonesystem must never attain such a high value as to interrupt altogetherthe flow of current across its moving contacts, it -will be seen that itis perfectly correct to substitute for the notion of a variableresistance, the idea of a variable conductivity. I

This interpretation of the phenomena of microphones suggests thepossibility of solving in a practical .manner the problem of thetelephone transmitter, without having recourse to .the use of carbon. IMoreover there lies at the back of this a theory of the microphone moregeneral than that based on the properties of carbon.

It suffices in fact to put in a state of vibration by the'action ofsound waves two or more movable contacts connected in a circuit, inorder to produce the microphone effect independently of the use ofcarbon, that is to say as a direct and immediate consequence of anyconductivity which is rendered variable. U

For example Branly has proposed a miby crossing three steel pointsinterconnected in a circuit.

Maj orama has constructed a liquid micro- Great Britain, resid-- phoneand Professor Vanni has improved this up to a point of rendering itpractical.

Preece has succeeded in using as a microphone an incandescent plate ofplatinum, cooling it simply by the action of the voice upon it. Mercuryand metallic filings have also-been employed for providing a variableconductivity inseveral researches on microphones. In spite of theresults attained, the only microphones in practical use are those ofcarbon. Practical experience always proves the superiority of thisapparatus although theoretically any mass of variable conductivity mightform a perfect transmitter.

There is therefore reason to conclude that the theory of the variableresistance or rather conductivity isnot complete.

-Bearing in mind that Hugues has been able to hear with a carbonmicrophone, using it'as a receiver, one may afiirm-that the microphonephenomena are much more complex than they appear to be at first sight,just as are all the phenomena of telephony. Many experiments havesuggested to Mr. Alexandre Vaugean the idea that the electric currentafiects in a special manner the media constituting the imperfectconductors (the variable resistances) and" that .the presumed action ofthe currents on the said media is favorably affected by the extrememobility of their points of contact. Hence he has been led to.constructa special microphone forming the subject of the present invention, andusing carbon in a manner which is novel from two points of view asfollows 1. The carbon elements are inclosed in a lass receptacle whichhas been evacuated in order to prevent heat losses due to conductivity.

2. The receptacle is suspended in. such a manner that it may vibrateintensely under the action of the shocks of the sound waves.

The suppositions have been abundantly confirmed in practice.

The passage of the current across the resistance of the. carbon effectsa physical modification of this element consisting in an extremelyattenuated and extremely slight pulverization of its superficial layers.

The particles detached by the action of the current on the carbon massesand projected outwardly create a special medium endowed with actualconductivity.

As the positionof the carbon elements in space is modified by the actionof the sound, the topography'of the zones of pulverized matter ismodified at the same time thus modifying also the action of the elementas a riability of resistance.

The absence of air (havmg as a result the avoidance of mechanicalresistance) favors on the'one hand the formation of a zone of specialconductivity and the extreme sensitivene'ss of the system "of suspensionof the new microphone, and facilitates on i the other hand thetransmigration of thezones ofdetached matter, which represent in factthe zones of variable resistance.

- The "realization of these two conditions assures superiority inresults attained according to the present invention, and at the sametime makes it possible to establish a more complete theory of themicrophone.

, The microphone may be regarded in, fact,

as the seat. of a miniature replica (because the phenomenon is much lessintense), of what takes placein an arc lamp wherein there isfa stream ofparticles detached by theaction of the current .and carrying the currentfrom. the one carbon poleto the other. The multiplication of the pointsof contactand the weakness of the currents employed in telephony preventan'y: appreciable degradation or wasting away of the positlye' poles orth'e transportation" of, pul-' verlzed matter to the negative p -leanThe slight amounts of matter detached irom the masse's'create so tospeak bridgesqofjgreater or less conductivitybetween thee ements whichhave come into imperfect 'contact one.

' with another.

' This new interpretation "may'j be summed up briefly. as follows v Thephenomena of the microphone result from the passage of an electriccurrent across ephemeral conductors, Whose value is extremely variable,and which are created by the said currents due to the partialdissociatlon of certain conducting massessuch as carbon, metallicfilings and so forth.

This theory explains in a manner which is quite satlsfactory, themicrophone of Preece using theincandescen plate, in view of the factthat the science of physics has proved long ago the presence of materialparticles in the flame or in the immediate neighborhood of'incandescentbodies.

011 the other hand if one may hear sounds by' means of a microphone, asstated by Hugues, Siemens, and so forth, it is in View of thebombardment of the particles detached from the carbon against thediaphragm. a i

In the accompanying drawings Figure 1 shows a microphone formed of acapsule or cell of glass suspended by three coil springs.

Fig. Qshows a section on the line ATB of Fig. 1. 4

Fig. 3 shows a microphone composed of three glass capsules connected oneto another and to the periphery of the casing or sound reflector by anarrangementof elastic members.

Fig. 4 is a section on the line CD of Fig. 3. i

Fig. 5 showsa transmitter composed of fourmicrophone capsules ofdiiierent construction supported by an elastic suspension.

Fig. 6 shows a section on the line E-F" of Fig. '5. 1

Fig. 7 shows a microphone composedof six capsules. 1

"Fig. 8 is a section on the line G-H of 7 i nFigs. 1, 2, 3 and 4, 1 is acapsule of glass into which have been sealed the pieces of metal or ofcarbon 2 and 3 which form the; poles of the microphone. 4 is a small lugor hook formed in the mass of the glass and coinciding with the littletube by whichsurface. The constmicti'on'of. Figs. 3 and 4' only difi'ersfrom that of Fig.1 in that three capsules are used.

In the form of construction shown in 1 Figs. 5 and 6, 7 and 8', themicrophonev has four and six ca sules respectively, these capsules"-bein difle'rently constructed from those described above; As isseen inFigs.

5 and 6 the capsule 9 containing the carbon is in this case made u' .oftwo face members 9 and 9 (Fig. 6). he ribs or projections 10, 11 and 12formed on each face ofa cen tral member so arate the cells 13, 14, and15 in which the 'ttle spheres of carbon are .placed. The carbon plates16 and" 17 are isolated from the capsules b means of ebonite annuli l8and periphera rings 19. The covers 20and 21 hold these elements of theapparatus, locking the plates in position, belng held together by thescrews22.

The. central s rings 23 connect together the capsules, (Figs. 5 and 6)or connect the surrounding capsules to the central one (Figs. 7 and .8),while the outer springs 2% connect the capsules to the periphery of thereflector.

In view of their respective positions, and of the fact that theyaremnder a suiiicient tension, the springs assure the elastic suspensionof the microphone capsules. At the least displacement of the layers ofair by means of the emission of sound, the system begins to vibrateunder the action on the one hand of the waves of sound which strikeagainst the front faces of the capsules, and on the other hand of thewaves of sound reflected from the rear by the reflecting surface, anddirected against the rear faces of the same capsules.

The various capsules are connected in parallel, one of their poles (thepositive pole) being formed by the carbon plate insulated from thecover, while the second pole (the negative) is formed by the coversthemselves. capsules are easily connected by connecting the springs bymeans of which the covers are supported.

It will be understood readily that any number of capsules may becombined in one instrument according to requirements and that thecapsules may have the carbon spheres at one face. only or at both facesas in Fig. 6, in which case they are placed in front of a reflector suchas 8.

The negative poles of the various Having thus described our inventionwhat we claim as new and desire to secure by Letters Patent is 1'. Amicrophone cell comprising two face plates and means for securing themto-.

gether, a central member with partition ribs thereon, plates of carbonand means for supporting them with insulation within the face plates,and a plurality of spheres of carbon in the compartments of the cellformed by the ribs, the said spheres of carbon being in light contactwith the carbon plates and with the central ribbed member of the cell.

2. A microphone for use in telephony comprising in combination anevacuated capsule, positive and negative terminals fixed therein, aplurality of small pieces of carbon within the capsule and in lightcontact with one another, and with the terminals and resilient means bywhich said capsule is supported, said means permitting said capsule tomove with an equal degree of freedom in all directions.

In testimony whereof we afiix our signatures in presence of twowitnesses.

ALEXANDRE VAUGEAN. ANTHONY on LAVANDEYRA. WILLIAM GARTHWAITE.

Witnesses:

CHAS. P. PBESSLY, MIGUEL FEROLO.

